In present day building construction, the majority of the cost of wiring is for transmission of high voltage electricity (e.g. exceeding 110 volt alternating current). Switched high-voltage circuits for residential, commercial and industrial wiring all include a power source that connects the power source in a loop with the load and a switch. For example, in residential wiring a ceiling light is connected to a circuit breaker box for power and a switch for control that creates a long run of high-voltage wiring in the wiring loop. The length of wire used can vary greatly depending on the position of the switch and the number of switches used.
When multiple switches are used to control a single load, such as a ceiling light, each of the switches must also be connected to one another by high-voltage wiring. Also, when installing multiple switches for a single load, the switches themselves are more expensive and it becomes exponentially more difficult for each additional switch. For this reason, most residential wiring does not exceed using two three-way switches to control a single load.
Modern electrical wiring codes rate wiring material by the circuit voltage, temperature and environmental conditions. High-voltage wiring is required by code to have sufficient gauge and insulation to carry the required current and provide fire safety. Generally, this high-voltage wiring is a solid wire with a plastic insulation that is not very flexible. This makes the wiring expensive and the installation difficult. Low-voltage wiring code requirements by contrast allow for thinner wire and insulation because there is less safety risk with lower-voltage wiring.